Outdoor shelter structures, such as portable outhouses, are commonly rented and used for special events, such as parties, festivals or concerts, as well as at job sites or other locations where people are gathered temporarily. These shelters are moved to and from the site on a truck typically, and while at the site they may be pumped out occasionally, to empty their septic tanks. While at the site, they must be stable, and not susceptible to tipping over, or being tipped over by the wind or by vandals.
These shelters must be rugged and durable, and since they must be moved manually, most operators who rent these out (a.k.a., pumpers) prefer them to be light in weight. A minority want them heavy, so as to counter any tendency to tip over. The buildings must be movable on and off of the truck, but once off of the truck, a single person should be able to move the building across the ground to position it in the desired location. The buildings also must be low in cost.
It is common to form much of these outdoor shelters of plastic resin. One exception, however, has been the base on which the remainder of the building is built. The bases are typically a composite structure of plastic and wood. The bases also usually have several main structural components, which can adversely affect their strength and rigidity.
Another common problem has been the connections between the shelter walls and the base. While plastic components in the base are preferable to wood for aesthetics, cleanliness and durability, the fastener holding ability of plastic base components has often been lacking. Sheet metal screws are typically used to secure the shelter walls to the base. The stresses at these fastener locations can be great when moving the shelter, under heavy winds, or when forces are applied to the walls, especially with a person in the shelter or with a full septic tank. Failure of the base to hold the fasteners can result in troublesome or costly repairs or complete replacement of the base or whole shelter.